ImmunoGen Reports Recent Progress and 2018 Operating Results

Sale of Kadcyla® Royalty Tail for $65
Million Further Strengthens Financial Position

Conference Call to be Held at 8:00 a.m. ET Today

WALTHAM, Mass.–(BUSINESS WIRE)–ImmunoGen,
Inc., (Nasdaq: IMGN), a leader in the expanding field of
antibody-drug conjugates (ADCs) for the treatment of cancer, today
reviewed recent progress and operating results for the quarter and year
ended December 31, 2018.

“We generated significant momentum in the business during 2018, led by
the completion of enrollment in FORWARD I, our registration study for
mirvetuximab soravtansine in platinum-resistant ovarian cancer; the
publication of combination data in over 100 patients to support label
expansion; and the advancement of our earlier-stage portfolio,” said
Mark Enyedy, ImmunoGen’s President and Chief Executive Officer. “On the
strength of this performance, we enter 2019 poised to deliver on a
number of important catalysts for the company, including top-line
results from FORWARD I in the first half of the year, the potential BLA
and MAA submissions for mirvetuximab monotherapy in the second half of
the year, and additional combination data from our triplet in
platinum-sensitive disease. Beyond our lead program, we expect to report
data from expansion studies in AML and BPDCN with our programs targeting
hematological malignancies and to file an IND before year-end for
IMGC936, an ADAM9-targeting ADC being developed in collaboration with
MacroGenics. Finally, with the benefit of the sale of the Kadcyla
royalty tail, we start the year with roughly $325 million on the balance
sheet to support our development and pre-commercial activities as we
transition to a fully-integrated company.”

RECENT PROGRESSMirvetuximab Soravtansine

Validation runs were successfully completed and commercial drug
product is now in inventory.

Initial safety and preliminary anti-tumor activity from the FORWARD II
expansion cohort assessing mirvetuximab in combination with Merck’s
anti-PD-1 therapy, Keytruda® (pembrolizumab), were
presented at the European Society for Medical Oncology (ESMO) 2018
Congress in October. Data from this cohort confirm the activity of
mirvetuximab in heavily pretreated platinum-resistant ovarian cancer,
with a trend toward longer duration of response with the combination
than would be expected for mirvetuximab monotherapy. Maturing data
from this cohort will guide further development of this novel
combination.

Encouraging initial data from the Phase 1 study of IMGN632 in patients
with relapsed or refractory adult AML and blastic plasmacytoid
dendritic cell neoplasm (BPDCN) were presented at the American Society
of Hematology (ASH) Annual Meeting in December. IMGN632 displayed
anti-leukemia activity across all dose levels tested and a tolerable
safety profile at doses up to 0.3 mg/kg. Enrollment in expansion
cohorts is ongoing to identify the recommended Phase 2 dose and
schedule for both AML and BPDCN.

Updated data from the IMGN779 Phase 1 dose finding study in AML
patients were also presented at ASH. These data show that IMGN779
continues to display a tolerable safety profile with repeat dosing
across a wide range of doses on the two schedules explored in patients
with relapsed AML, with anti-leukemia activity seen in both schedules.
Enrollment is ongoing to identify the recommended Phase 2 dose and
schedule.

IND-enabling activities were initiated during the quarter for IMGC936,
a novel ADAM9-targeting ADC being developed in collaboration with
MacroGenics.

Multiple abstracts highlighting platform innovations were submitted
for presentation at the 2019 Annual Meeting of the American
Association for Cancer Research.

Operational Updates

Commercial planning and launch readiness activities for mirvetuximab
have been initiated to support a potential launch in 2020.

Earlier this month, ImmunoGen announced the sale of residual rights to
receive royalty payments on commercial sales of Kadcyla
(ado-trastuzumab emtansine) to the Ontario Municipal Employees
Retirement System (OMERS), the defined benefit pension plan for
municipal employees in the Province of Ontario, Canada, for $65
million.

ANTICIPATED 2019 EVENTS

Report top-line results from Phase 3 FORWARD I trial of mirvetuximab
in platinum-resistant ovarian cancer in the first half of 2019,
followed by full FORWARD I data presentation at a medical meeting;

FINANCIAL RESULTSRevenues for the year ended December 31,
2018 were $53.8 million, compared with $115.4 million for the year ended
December 31, 2017. License and milestone fees of $15.3 million for 2018
included $13.8 million of recognized upfront fees previously received
from partners and $1.5 million in partner milestone payments. This was
compared to license and milestone fees of $79.5 million for 2017, which
included a $30 million paid-up license fee related to an amendment to
the Company’s collaboration and license agreement with Sanofi, $29.5
million related to the sale and transfer of the Company’s IMGN529 asset
to Debiopharm, $7 million in partner milestone payments, and $12.7
million in amortization of a non-cash fee related to the Company’s
license agreement with CytomX. Revenues for 2018 included $32.5 million
in non-cash royalty revenues, compared with $28.1 million for 2017.
Revenues for 2018 also included $1.4 million of research and development
(R&D) support fees and $4.6 million of clinical materials revenue,
compared with $3.5 million and $4.4 million, respectively, for 2017.

Operating expenses for 2018 were $214.3 million, compared with $174.4
million for 2017. The increase was driven by R&D expenses, which were
$173.9 million for 2018, compared with $139.7 million for 2017. This
increase was primarily due to higher external manufacturing costs and
third-party service fees in support of commercial validation for
mirvetuximab soravtansine, along with higher clinical trial costs
related to the FORWARD I, FORWARD II, and IMGN632 studies and, to a
lesser extent, an increase in stock-based compensation. General and
administrative expenses for 2018 increased to $36.7 million, compared to
$33.9 million for 2017, primarily due to increased third-party service
fees and stock-based compensation. Operating expenses for 2018 also
included a $3.7 million restructuring charge due to the previously
announced decommissioning of the Company’s Norwood facility, compared to
a $0.8 million charge in 2017 related to a loss recorded on leased
office space.

ImmunoGen reported a net loss of $167.9 million, or $1.20 per basic and
diluted share, for 2018, compared with a net loss of $96.0 million, or
$0.98 per basic and diluted share, for 2017. Weighted average shares
outstanding increased to 139.9 million in 2018 from 98.1 million in 2017.

ImmunoGen had $262.3 million in cash and cash equivalents as of December
31, 2018, compared with $267.1 million as of December 31, 2017, and had
$2.1 million of convertible debt outstanding in each period. Cash used
in operations was $166.4 million for 2018, compared with cash provided
from operations of $7.6 million for 2017. The prior period benefited
from a $75 million upfront payment received from Jazz Pharmaceuticals,
and $59.5 million of fees received from Sanofi and Debiopharm. Capital
expenditures were $5.2 million and $1.1 million for 2018 and 2017,
respectively.

FINANCIAL GUIDANCEFor 2019, ImmunoGen expects:

cash and cash equivalents at December 31, 2019 to be between
$135 million and $140 million;

revenues between $40 million and $45 million; and

operating expenses between $265 and $270 million.

ImmunoGen expects that its current cash combined with the expected cash
receipts from partners and collaborators will enable the Company to fund
its operations at least a year beyond the release of top-line results
from the Phase 3 FORWARD I trial, which are expected in the first half
of 2019.

CONFERENCE CALL INFORMATIONImmunoGen will hold a conference
call today at 8:00 am ET to discuss these results. To access the live
call by phone, dial 323-794-2093; the conference ID is 6271602. The call
may also be accessed through the Investors section of the Company’s
website, www.immunogen.com.
Following the live webcast, a replay of the call will be available at
the same location through February 22, 2019.

ABOUT IMMUNOGENImmunoGen is developing the next generation
of antibody-drug conjugates (ADCs) to improve outcomes for cancer
patients. By generating targeted therapies with enhanced anti-tumor
activity and favorable tolerability profiles, we aim to disrupt the
progression of cancer and offer our patients more good days. We call
this our commitment to “target a better now.” Our lead product
candidate, mirvetuximab soravtansine, is in a Phase 3 study for folate
receptor alpha (FRα)-positive platinum-resistant ovarian cancer, and in
Phase 1b/2 testing in combination regimens. Our novel IGN candidates for
hematologic malignancies, IMGN779 and IMGN632, are in Phase 1 studies.

FORWARD-LOOKING STATEMENTSThis press release includes
forward-looking statements based on management’s current expectations.
These statements include, but are not limited to, ImmunoGen’s
expectations related to: the Company’s revenues and operating expenses
for the twelve months ending December 31, 2019; its cash and marketable
securities as of December 31, 2019; the occurrence, timing and outcome
of potential pre-clinical, clinical and regulatory events related to the
Company’s and its collaboration partners’ product programs; and the
presentation of preclinical and clinical data on the Company’s and
collaboration partners’ product candidates. For these statements,
ImmunoGen claims the protection of the safe harbor for forward-looking
statements provided by the Private Securities Litigation Reform Act of
1995. Various factors could cause ImmunoGen’s actual results to differ
materially from those discussed or implied in the forward-looking
statements, and you are cautioned not to place undue reliance on these
forward-looking statements, which are current only as of the date of
this release. Factors that could cause future results to differ
materially from such expectations include, but are not limited to: the
timing and outcome of ImmunoGen’s and the Company’s collaboration
partners’ research and clinical development processes; the difficulties
inherent in the development of novel pharmaceuticals, including
uncertainties as to the timing, expense and results of preclinical
studies, clinical trials and regulatory processes; ImmunoGen’s ability
to financially support its product programs; ImmunoGen’s dependence on
collaborative partners; industry merger and acquisition activity; and
other factors more fully described in ImmunoGen’s Annual Report on Form
10-K for the year ended December 31, 2017 and other reports filed with
the Securities and Exchange Commission.